The synthesis and photoluminescent properties of calcium tungstate nanocrystals

CaWO₄ nanocrystals with average diameters of 20-30 nm and nanorods with mean lengths of 600-1000 nm were controllably synthesized through a facile microemulsion-mediated hydrothermal procedure. And the factors affecting the morphologies of the products, such as the molar ratio (w) between water and CTAB, the reaction temperature and the concentration of the reactants, were studied and discussed. With the increase of the w value, the diameter of the as-synthesized products increased gradually, except in the case of w=10 where nanorods were formed. With the temperature increasing, the morphologies of the products changed from nanocrystals to nanorods, and finally to nanocrystals again. However, the concentration of the reactants exhibited no obvious influence on the shape and size of the CaWO₄ product. A possible mechanism is proposed for the selective formation of the different morphologies. The photoluminescent properties of the CaWO₄ nanocrystals are also reported. All the products of CaWO₄ with different morphologies exhibited the only green peak at 435 nm with an excitation wavelength at 238 nm.